The Utility of Saliva Samples for Mass Population COVID-19 Screening
Saliva samples solve several challenges inherent to nasopharyngeal swabs
Dr. Moemen Abdalla is the director of marketing and sales and one of the senior scientists at Norgen Biotek Corp. Dr. Abdalla obtained his masters in biochemistry at Alexandria University, Egypt, and completed his PhD in biotechnology at Brock University, Canada. 11 years ago, Dr. Abdalla joined the team at Norgen Biotek, specializing in sample preparation and molecular diagnostics. During his time at Norgen, Dr. Abdalla has developed many leading-edge research and diagnostic tools for scientific use. This includes purification kits for RNA, DNA, and exosomes, as well as preservatives for sample collection of saliva, urine, and cf-RNA/cf-DNA. In the wake of the current pandemic, Dr. Abdalla perseveres along with his team, making significant contributions to Norgen’s comprehensive COVID-19 workflow.
Q: What are the limitations of nasopharyngeal and oropharyngeal swabs for COVID-19 testing?
A: Saliva is an extremely non-invasive collection method. You just need to spit, which anyone can do. It’s good for kids at schools, for seniors’ homes, for use at airports, and for patients with any issue that does not allow them to be swabbed. Another serious advantage of saliva collection is that you don’t need a nurse to be physically present to monitor the sample collection.
Q: How do saliva specimens solve some of these sampling challenges?
A: Saliva as a sample type can address the swab shortage issues that the world faced during the first wave. Lots of people couldn’t get tested, and we don’t need to have the same issues of shortages of chemicals and swabs preventing people from getting screened during the second wave, which has already started in several countries. Having an approved saliva-based test worldwide will expedite the results and ensure that lots of people get screened, especially kids and seniors. Saliva will be useful for mass population screening, which needs to be very fast and to cover a lot of people.
Currently, when swabs are collected and placed in media, the virus is alive and infectious. This increases the risk of frontline workers—nurses and doctors, for example—becoming infected. Norgen Biotek’s preservative for the saliva samples kills the virus instantly, which means the transport of the sample is safe.
Q: What are the limitations of saliva samples?
A: Saliva itself is a very complex sample because of the amount of proteins and bacteria and mucin present in the mouth. It’s easy to collect and it’s not infectious once you collect it on our preservative, but you have to have a good method to get the virus out for diagnosis.
At Norgen Biotek, we got around this problem by adjusting the procedure to make it easier to extract the viral RNA out of saliva.
Q: Can you describe the technology Norgen Biotek has developed for extraction of COVID-19 viral RNA from saliva?
A: We have a very well-optimized procedure, the Saliva/Swab RNA Purification Kit, which is based on our proprietary resin called silicon carbide. It is optimized to isolate the RNA virus from fresh or preserved saliva, and also to extract the viral RNA from swabs in universal viral transport media.
Norgen Biotek is the only company on the market that uses this silicon carbide for the isolation of RNA from viruses. It has many advantages over the commonly used silica-based technology, which is used in all of the other spin column and magnetic bead-based kits on the market.
If the virus is collected on a transport media that doesn’t preserve the sample, it will degrade the RNA—instead of being long, the RNA is going to be short fragments. The silica-based technology on the market has a hard time getting these short fragments of the RNA. With our silicon carbide technology, we don’t have any limitation to the size or sequence; it’s able to get any RNA, short or long, from the sample. Because the silica-based technology fails at getting a small-sized RNA, it runs the risk of false negatives. But with our procedure and silicon carbide technology, it will fish RNA out of the sample regardless of the size, so it’s going to call a true positive “positive” and a true negative “negative”.
Q: Can you describe Norgen Biotek’s COVID-19 saliva testing workflow?
A: The workflow starts with the collection of saliva on our preservative, which instantly kills the virus and preserves its RNA for two months at room temperature. That is useful in the case of backlogs of samples that have been collected but must wait to be processed. The second step of the workflow is the extraction of viral RNA from the sample, which is based on our silicon carbide technology. The third and final part of the workflow is the detection method. Currently Norgen Biotek has two detection methods: one based on the CDC-recommended primers that were published at the beginning of the pandemic and the other based on the WHO-recommended primers.
Norgen Biotek’s entire workflow, from collection to extraction to detection, is CE-IVD-approved. We are currently working on getting the entire procedure Health Canada-approved and FDA-approved.